Duplex telegraph system



May 30, 1950 P. YvEs MARIE LE CALVEZ 2,509,829

DUPLEX TELEGRAPH SYSTEM Filed Aug. 11, 1947 K/SO INVENTOR.

Philippe Y-ves Marie Le Cclvez Patented May 30, 1950 UNITED STATES .TENT QFFICE DUPLEX TELEGRAPH SYSTEM Application August 11, 1947, Serial No. 767,978 In France May 17, 1944 Section 1, Public Law 690, August 8, 1946 Patent expires May 17, 1964 2 Claims. (01. 178-58) This invention which relates to telegraph systems is for improvements in or modifications of the invention disclosed in my copending specification Serial No. 770,416, filed August 25, 1947, and entitled: fIelegraph system.

Said copending specification describes a telegraph system the chief characteristic of which lies in the positive checking by the transmitter of the correct reception of the previously transmitted signal before the transmission of the next signal. In the radio telegraph system therein described the signal correspondin to an element to be transmitted is decomposed into a predetermined number of elemental signals, each elemental signal being characterized by the transmission of one or the other of a pair of modulation frequencies Which is allotted to it, all these modulation frequencies being preferably sent on a single carrier wave. The positive checking is obtained by means of an additional modulation sent back over the oppositely directed channel of the duplex system, and finally the transmission of each signal is accompanied by another modulation, called the starting or identification frequency, which characterizes it.

The present invention seeks to provide simplified systems embodying the method described in said copending specification while retaining the advantages thereof the most important of which is, the maintaining of a very high degree of reliability or correctness of transmission Whatever the conditions of propagation.

As will be seen later the simplified systems of the invention allow duplex communication by using for the reverse or oppositely directed channel two other pairs of modulation frequencies one of which is used for the starting frequency and for the transmission of code signals, and the other for checking.

According to the present invention, use is made for the transmission of the identification or starting signal and of the elemental signals characterizing the element to be transmitted, of one pair of frequencies, one or other of said frequencies preferably modulating a transmitter of the telephone or modulated telegraphy type, and serving successively for the starting frequency and the signalling frequency proper. My copending specification describes, among other things, a system in which the various modulation frequencies are impressed on the carrier Wave consecutively by means of a distributor instead of simultaneously. The present invention provides improved systems of this nature which are simplified by reason of the use of only one pair of modulation frequencies.

The invention is illustrated in and further explained with reference to the accompanying drawings which show, by way of example, a preferred embodiment Figures 1 and 2 being, respectively, diagrams of the transmitter and of the 00- operating receiver.

In the drawings the radio circuits have been omitted as not forming per se, parts of the invention. The transmitter station (Fig. 1) com prises, as in my copending specification, a transmitter Tn importing different polarities to the leads I connecting it to the distributor 2. Five leads have been shown corresponding to a fiveunit code, but it will be obvious that the invention may be used whatever be the number of units in the code. that once started by the relay 3 its brush effects one and only one complete revolution from the inoperative position in which the brush is on contact P. Assuming l and 2 to be the checking frequencies transmitted over the reverse channel, and fl and f2 the pair of frequencies serving both as the starting and signalling frequencies, the reception of frequency actuates through leads 4 a relay 6 of the compensating winding type which becomes inoperative again in the absence of l. Similarly the frequency 22 actuates the symmetrical relay 1 through leads 5. It will therefore be seen that in the leads B--9 there will flow a current whose direction is characteristic of the frequency el or 2 received, the circuit in question being the same as the corresponding circuit of the arrangements described in my copending specification. The current flowing throughleads 8-!) actuates the relay 3 in the same manner whatever be its direction, and also actuates the relay ill, the armature of which imparts or polarity to the lead ll according to the directions of the current in 89, this relay I0 bein adjusted so as to be indifferent as to polarity. It will be seen that in this case also, in the case of fading or static, no current flows through 8 and 9, and consequently the relays 3 and I0 do not move.

The lead l is connected to the first contact Pl (after the dead contact P) of the distributor 2, and to a relay [2 with two contacts l3 and M. The lead H is connected to this end to the armature of the contact l3 and also to one end of the energization coil of relay I 2, the other end of which coil is connected to the armature of a second relay 15 which is adjusted so as to be indifferent as to polarity. Relay l5 imparts or' polarity to its armature according to the position thereof and the coil'of the said relay is con- The distributor is arranged nected between ground and the contact l3 of the relay l2.

Contact l4 controls the feed of the translating device Tn, as in the arrangement of the copending specification. When there is no current flowing through its energization coil the relay l2 has its contacts l3 and M open.

As is customary the and polarities are connectedto the :poles:

of the usual battery the mid point of which is grounded. This is also the case for Fig; 2.

A sufficient distance is provided between the contacts PI and P of the distributor 2 for the transmitter Tn to have time to change 'from'one combination to the other during the energization of 3 and the travel of the brush from the contact P to the contact Pl. I y

In Order to avoid too great a loss of time due to the inertia of the ordinary known band transmitters use may be made of a system of two transmitters which are alternately place d in communication with the distributor bymeans of a reversingswitch which can be controlled by the change ofpolarity of the armature of the relayl0. Inorder to obtain correct correlation atthe' receiving end two distributors may be usedsimilar-to the distributor 45- which may be alternately'connected-to the armatures of the relays 34 according to the polarity of the starting frequency received. V 7

The brush of the distributor 2 supplies through lead 'lli the energization coils of relays l1 and it of the compensated type, the other ends of these coils-being grounded. According to the polarity applied to the-lead lit-the relay l'! or the relay l8 becomesoperative, thereby imparting a, pre

determined polarity, for example to the lead 19, thus producing-transmission of frequency fl, or' totheconductor 29 to produce the transmission of the frequency f2. r

The operation of the transmitter is as follows? if the previous signal corresponding to the startingfrequency fl, for example has been correctly received, thechecking frequency l is returned and operates the relay l 0, which reverses the polarity in the lead I l.

forward atthe-same time causing it to prepare the next combination (as in the arrangement of the copending specification). Furthermore; by means eras contact l3-the relay l2 operates'the relay VI which, owingto this fact, places its armature. on the samepolarity as relay .lfi. It will therefore be seen that the checking frequency (pl is thus associated with the frequency fl (considered as the starting. frequency) and similarly At'the same timeias relay lll operates, the current in leads 89 operate relay 3, thereby starting the distributor2. The brush of distributor 2 as it passes over the contact Pl produces by acting on one of the relays l! or IS, the transmission of fl or f2 acting as'a starting frequency, and then, as it passes'over the five other contacts, the transmission of'fl or f2 acting'this time as a signalling frequency; this being 'eifected according to'the-polarity' impartedto the corre-" spondingleadl by'the translating device Tn.

Itwill be seen thatthese' starting and signal ling frequencies arethustransmitted in the 'form of successive pulses on the frequency fl o f2. The signal pulses are preferably of equal"dura-' tion whereas the starting pulse is of a substani-z As the relay l5 was pre viouslyin contact with the same polarity as re-' lay all),- a current passes through the coil l2' whereby said relay -l2'is operated, and by means of i'tscontact l4 feeds the translating device Tn" actuated by 'the'relay 3, and it therefore again returns the" previous character or type, with a preliminary starting frequency fl, thereby warningthe receiverthata repeat is being effected as will be seen hereinafter.

The receiver, Fig. 2, has a circuit comprising relays'2l and'22'and leads 23 and 24. The direction of the current flowing through leads 23 24' "characterizes the frequency fl or f2 received. These leads supply the coil of the relay 25 (which operates inwthe same manner whatever may bathe direction of the current which; flows through-Hit) and the coilof the relay: 26,-- which placesits armature on the or polarity according to the direction of -the-current-in its coil. The'armat-ure is connected to the brush of a distributor?fl similar to the-distributord of Fig; l and actu-ated'by- -the relayZB. Throughthe control of-relay 2B, the brush of distributor- 2 1- effects one eandonly -one complete revolution-- from its inoperative position on the contact (1:

In this inoperative position the brushshortcircuits the contacts "2 9 and 311 arranged on-the leads 3| -and 32-which will be referredto herein after. 7

The fivecontacts, excluding q, of the-distributor 21 are connected 'by the-leads-33 to the corresponding energization --coils of '-fivesimilar relays 34' and-of -five similar relays 35, =saidycoils for"the different contacts -being' connectedin series. The opposite ends-of" the coils 35 are connected in parallel tothelead 3h The-relaysBE-each havetwo contacts 36' and 31-. The contacts36; which are arranged inseries, form a chain, and their-simultaneous-1closurecausespas will-be seen from the drawing -the energization of the coil of a relay 38.- The relays" 35-have a second windingconnected between ground and armature of the contacts 31,- saidcontacts being connected in parallel to the lead 39.-- The relay 38 has two contacts, one a single contact 40, the other-double contacts 4l.- Ac-- cording as to whether the relay 38 is inoperative or operative, the armature of the contacts 4i im-- parts-a predetermined polarity, for example negative polarity to the upper contact connected: to the lead 39 or tothe lower contact connected to the lead 42 supplying a relay 43 actuating'a second distributor 44 with a brush 45 connected to the line 46.

The relays 34', according to the direction of thecurrents which now through themfplace their' armatures on their positiveor negative contacts- These armatures are connected bythe leads dltothecorresponding contacts of the distributor 44; The lead 48 connects the dead contact q-offthe distributor 21' to the contact 40 of relay 38. A

condenser d9 of appropriate capacity is connected between the leads 3! and 48. The'coil of a relay 50, which is not polarized, is connectedbetween the lead 3| and the armature of the contact 40. According to the direction-of the currentflowing through its'coil, said relay-50 imparts'a positive" or negative polarity to its armature connected" to the'lead' 32 which'supplies, through the con tacts 30, the coils of the relays il and- 52 th armatures of which, according to the direction of the current flowing through said coils, impart a predetermined polarity, for example the negative polarity, either to the lead 53 controlling the transmission of the checking frequency or to the lead 54 controlling the transmission of (p2. The distributor 44 is provided, before and after the contacts to which the leads 4? are connected, with two additional contacts TI and 11, connected in a fixed manner to predetermined polarities for a purpose which will be explained hereinafter.

The receiver operates as follows:

When there is no signal as in the case of static or fading, no current flows through the coils of relays 25 and 26. As soon as the starting frequency is received the relay 25 attracts its armature whereby a current flows through the coil 28 (the contacts 29 being closed since the distributor 21 is on the inoperative contact q). Relay 2B is delayed so that it only operates if the pulse received has a suificient duration, thereby preventing its confusion with a signalling pulse which is too short to actuate it. At the same time the condenser 49 is charged with a polarity which is determined by the position of the armature of relay 26, i. e. by the frequency fl or f2 received. As soon as the relay 28 operates, the distributor 21 starts rotating at the same speed as that at the transmitting station. For each contact passed over from q the relay 25, if the transmission is correct, connects the leads 3| to earth, while 26 connects the suitable polarity in turn to each lead 33. Consequently the circuit 33, 34, 35 and 3| is closed, the relay 34 involved places its armature in the corresponding position and the selected relay 35 attracts its armature and closes the contacts 36 and 31. By means of the contacts 31, the relay 35 is locked, its hold-on coil remaining energized since the relay 38 is as yet inoperative.

If, at the completion of the rotation of the distributor 21, all the pulses have been received, the chain of contacts 36 is complete so that the relay 38 operates and attracts its armature.

The relay 38, by means of the lower contact 4|, sets in operation the relay 43 which actuates the distributor 44 which, by its rotation, reads the polarities imparted by the relays 34 to the leads 4'! and successively returns them through the line 46 to the translating device involved which has previously been set in operation by the wiper of distributor 44 passing over the first contact rl connected to a predetermined polarity and which stops as said wiper passes over the contact 1*! which is also connected to a fixed polarity. By the closing of the contact 40, the relay 38 further causes the discharge in a predetermined direction of the condenser 49 through the coil of the relay 50. This relay operates, and, contacts 30 being closed since 21 has become inoperative again, a predetermined polarity is imparted to the coils of relays and 52, whereby one of the said relays operates and the checking frequency (pl or (p2 is transmitted.

Finally the relay 38, by the operation of its armature 4|, cuts off the supply to the hold-on coils of the relays 35. These five relays therefore return to their inoperative position.

If on the contrary one (or several) signalling frequencies has not been received the corresponding relay 35 remains open with resultant nonclosing of the contact chain 36. It follows that relay 38, and consequently relays 43 and 50, do not operate, and consequently as soon as the distributor 21 returns to its inoperative position (on the contact q) it is the same lead '53 or 54 which remains connected to the polarity in the drawing) of the armature of the relay 5| or 52. Since distributor 21, as it returns to its inoperative position, produces the transmission of the checking frequency, it follows that it is the same frequency which is returned a second time. This involves the repetition by the transmitter of the sending of the character or type previously transmitted. At this instant it is only necessary for the relays 35, which had not been operated the first time, to be actuated for the chain 36 to close, thereby producing the change of the checking frequency.

Distributors have been described both at the transmitting end and at the receiving end comprising as many contacts for the signalling as the code used comprises units (five in the drawings). It is obvious that it is possible to group several characters or types to be transmitted. For example, with a five unit code it is possible to use distributors with 4 5=20 signalling contacts by sending four characters in the same cycle. The operation and the apparatus is not changed, and a four-channel multiplex system is thus obtained.

Many modifications may be made to the embodiments described without departing from the scope of the invention.

What I claim is:

1. In a duplex telegraph system, the combination of a transmitter including a control circuit adapted to be energized in either direction, a relay adapted to be energized by said circuit, a main operative circuit for the transmitter the polarity of which is defined by said relay in accordance with the polarity of the control circuit, means: whereby said main operative circuit controls the emission of the transmitted signals, a relay energized by said operative circuit, a distributor controlled by last mentioned relay and adapted to transmit first, a comparatively long signal for identification that is selected alternately from each of a pair of predetermined frequencies for the successive character signals and second, the elemental signals of the character signal, each of said elemental signals being selected according to a predetermined code from the frequencies of said pair of predetermined frequencies, and a receiver includin means for receiving the signals transmitted by the transmitter, a main operative receiver circuit, switches inserted in series therein, relays energized by the successive incoming elementary signals, means whereby said switches remain closed until the succession of elemental signals has been received and means whereby the main operative receiver circuit closed by the closing of said switches controls the emission of a control signal that is alternately emitted on two frequencies of a second pair of frequencies and means whereby the arrival of a control signal energizes the transmitter control circuit with a predetermined polarity that changes from one control signal to the next.

2. In a duplex telegraph system the combination of a transmitter having means to transmit for each character signal a comparatively long identification signal at a frequency that changes from one frequency to another of a pair of frequencies between the transmission of one character signal and the next character signal, said transmitter also having means for transmitting a coded signal constituted by a succession of short pulses selected from said pair of frequencies and a receiver including a receiver circuit adapted to be energized with an electrical polarity deter- 7 mined by the frequency transmitted by'the' transmitter', a firstdis'tribiito'rcontrolled by-the energization -of" said circuit at the reception of the identification signal, said -first' distributor provi'ded with'a plurality'of contactpieces; a second distributor, a first'and-a second 'set ot-relays in series with each of said contact'pieces" of said first distributor} means whereby the 'said'first set of relays control the polarity of the contact pieces of said seconddistributbhhold up windingsfor said 'second 'setofhrelays;a main operative receiver circuit; "a plurality of switches in saidmai'n operative circuit" adapted 'to be 'closedbyth'e energization of the corresponding 'ones'bfsaid second: set rel'ays 'and-"means whereby the energizatio'nof the operatii e circuit through the closmg of the corresponding "ones' ofsaid "switches controls the polarities ofsaid-"contact pieces of the second distributor; fo'rsaid mission of the control signals on one of two frequencies falter nately with one another from one character signal to the next and for the deenergization of said hold up windings for said second relays; v

PHILIPPE YVES MARIE LE CALVEZ.

REFERENCES CITED UNITED STATES PATENTS- Name Date Bakker et 'al. Max-:18, 1941 Number 

